Republican mayoral hopefuls Joe Lhota and George McDonald are the only two in a crowded field of candidates who support Hizzoner’s hard line of not negotiating with striking school-bus workers.

Lhota (pictured) yesterday called the demands by Local 1181 of the Amalgamated Transit Union for job protections given only to public employees a “very, very slippery slope that we go down.”

“They’re private-sector workers, but they want the same benefits and everything else that goes on that you would have at the Transit Authority . . . The mayor is absolutely correct,” Lhota said on WNYW/Channel 5’s “Good Day, New York.”

“The courts have held that what the union is asking for is illegal,” he added.

McDonald, founder of the Doe Fund, said he’d go even further by giving the strikers 48 hours to return to work or else he’d accelerate the bidding process that set them off in the first place.

The city has cited a 2011 New York appeals court ruling that deemed the job protections the union wants to be illegal.